A comparison of frequencies between mouse T cells and B cells which are mutually interactive and specific to each other.

Repertoire sizes of T cells and B cells were estimated by frequency studies using mouse helper T cell clone D10G4.1 (D10 for short) and monoclonal antibodies raised against the antigen recognition structures on D10 cells. The soluble form of these antibodies was capable of activating D10 cells to proliferate in the presence of exogenous IL-1. Moreover, among the heterogeneous peripheral T cells, there is a population of cells which respond to those antibodies. Normal spleen B cells were non-clonally activated by LPS in limiting dilution cultures and the supernatant was tested for its activation capacity on D10 cells. Precursor frequencies of B cells which produce D10 activating antibodies were in the range of one in millions. The presence of D10 cells in the limiting dilution cultures increased this frequency by a factor of more than ten. For the estimation of frequencies of a given T cell clone which is activated by anti-D10 antibodies, normal spleen T cells were activated either by beads coupled monoclonal antibodies or by Con A followed by specific soluble antibodies in the limiting dilution cultures, and thereafter specific proliferation was assayed. A group of monoclonal anti-receptor antibodies gave rise to a single hit curve with relatively low frequency of one in 10(4) to 10(5). Another group of antibodies revealed in addition to the low frequency population, a higher frequency population of one in thousands. The data taken together suggest the frequencies of mutually interactive B and T cells are in the range of one in 10(4) to 10(5), while among T cells, there can be seen another population of cells of ten to a hundred fold higher frequency. Consequently, direct idiotype-antiidiotypic interactions between lymphocytes should occur only once in 10(8) to 10(10) cells in the normal unstimulated immune system. Thus, it is more likely that interactions will take place between cells of more degenerated specificities. The implications of these findings in favour of multiple levels of connection among T cells which reflect the multiple levels of affinity of the recognition complex of T cells are discussed.